Research reportPositive reinforcing effects of RFamide-related peptide-1 in the rat central nucleus of amygdala

- RFRP-1 belonging to the RFamide peptide family was microinjected to the amygdala.
- The lower dose of RFRP-1 induces place preference, while higher dose is ineffective.
- NPFF receptor antagonist RF9 pretreatment prevents positive reinforcing effects of RFRP-1 in the central nucleus of amygdala.
- These results are the first to show rewarding effects of RFRP-1 in the amygdala.

The amygdaloid body (AMY) plays an important role in memory, learning and reward-related processes. RFamide-related peptide-1 (RFRP-1) immunoreactive fibers and NPFF1 receptors were identified in the AMY, and previously we verified that neuropeptide RFRP-1 infused into the central nucleus of AMY (CeA) caused food intake decrease. The aim of the present study was to examine the possible rewarding or aversive effects of RFRP-1 in the CeA. In conditioned place preference, test male Wistar rats were microinjected bilaterally with 50 or 100 ng RFRP-1 in volume of 0.4 μl. In other groups of animals, 20 ng NPFF receptor antagonist RF9 was applied or the antagonist was used 15 min before 50 ng RFRP-1 treatment. Fifty nanograms of RFRP-1 had positive reinforcing properties, while 100 ng RFRP-1 had no effect. Prior treatment with NPFF receptor antagonist RF9 could block the rewarding effects of RFRP-1, while the antagonist applied alone did not influence the behavior of rats in place preference paradigm. Our results show that RFRP-1 and NPFF-1 receptors play important roles in the amygdaloid rewarding-reinforcing mechanisms.